Welcome to the forums from across the pond. You own my favorite trailer. I still miss my Tradewind and maybe someday when I have the room will buy another one just to play with. I agree they are nicer than the new ones.
My suggestion with the window is to carefully remove the inside window. Once it breaks it can not be replaced with a double pane window, the replacement is a single pane. Be careful to mask off all of the glass and have a good tarp down. The glass will break into thousands of little balls, if taped well enough it will hold together when you remove it.
Good luck to you. Let me know if you ever come camping on this side of the lake?
1994 30' Excella 1000, Chummy III- Ford Excursion- 7.3 Turbo-diesel